One valid objection that came up in the comments is that calorie-controlled diets in a research setting may not reflect what happens in real life. For example, in a context where calorie intake isn't tightly controlled, diet composition can impact calorie intake, in turn affecting body fatness. This, of course, is true, and it forms one of the central pillars of our fat loss program the Ideal Weight Program.

Some low-carbohydrate diet advocates argue that the obesity epidemic was caused by US dietary guidelines that emphasize a carbohydrate-rich diet*. The idea here is that the increase in calorie intake was due to the diet shifting in a more carbohydrate-heavy direction. In other words, they're hypothesizing that a carbohydrate-rich eating style increases food intake, which increases body fatness**. According to this hypothesis, if we had received advice to eat a fat-rich diet instead, we wouldn't be in the midst of an obesity epidemic.

Fortunately for us, this hypothesis has been tested-- many times! Which eating style leads to higher calorie intake and body fatness when calories aren't controlled: a carbohydrate-rich diet, or a fat-rich diet?